array_sum（）到数组中的值

How can i add array_sum to the string in my loop without making another foreach loop for it? I am trying to combine all of the numbers together instead of having this multi dimensional array and then just have the value and i see that array_sum wont add them up because its inside of an array. any ideas?

$hours_arr = array();
foreach($proj_time as $item){
    $hours_arr [$item['project_id']]['item_value'] = $item['item_value'];
    $hours_arr [$item['project_id']]['hours'][] = $item['hours'];
}

//output
array (size=3)
  4 => 
    array (size=2)
      'item_value' => string 'Coaching' (length=8)
      'hours' => 
        array (size=1)
          0 => string '999.99' (length=6)
  1487 => 
    array (size=2)
      'item_value' => string 'Standby' (length=7)
      'hours' => 
        array (size=1)
          0 => string '15.00' (length=5)
  1488 => 
    array (size=2)
      'item_value' => string 'Standby' (length=7)
      'hours' => 
        array (size=4)
          0 => string '10.00' (length=5)
          1 => string '10.00' (length=5)
          2 => string '10.00' (length=5)
          3 => string '10.00' (length=5)

I would like my output to be

1488 => 
    array (size=2)
      'item_value' => string 'Standby' (length=7)
      'hours' => string '40.00' (length=5)

edit: added contents of $proj_time

Array
(
    [0] => Array
        (
            [project_id] => 4
            [consultant_id] => 51
            [engagement_id] => 8
            [hours] => 999.99
            [item_value] => Coaching
        )

    [1] => Array
        (
            [project_id] => 1487
            [consultant_id] => 1
            [engagement_id] => 1
            [hours] => 15.00
            [item_value] => Standby
        )

    [2] => Array
        (
            [project_id] => 1488
            [consultant_id] => 31
            [engagement_id] => 7
            [hours] => 10.00
            [item_value] => Design App RFP
        )

    [3] => Array
        (
            [project_id] => 1488
            [consultant_id] => 32
            [engagement_id] => 41
            [hours] => 10.00
            [item_value] => Training
        )

    [4] => Array
        (
            [project_id] => 1488
            [consultant_id] => 55
            [engagement_id] => 41
            [hours] => 10.00
            [item_value] => Training
        )

    [5] => Array
        (
            [project_id] => 1488
            [consultant_id] => 1
            [engagement_id] => 1
            [hours] => 10.00
            [item_value] => Standby
        )

)

Instead of creating array and then applying operation, while creating itself why don't you sum up like this:

DEMO

$hours_arr = array();
foreach($proj_time as $item){
    $hours_arr [$item['project_id']]['item_value'] = $item['item_value'];
    if(array_key_exists('hours', $hours_arr [$item['project_id']]))
        $hours_arr [$item['project_id']]['hours'] += $item['hours'];
    else
        $hours_arr [$item['project_id']]['hours'] = $item['hours']; 
}

Result:

Array
(
    [4] => Array
        (
            [item_value] => Coaching
            [hours] => 999.99
        )

    [1487] => Array
        (
            [item_value] => Standby
            [hours] => 15
        )

    [1488] => Array
        (
            [item_value] => Standby
            [hours] => 40
        )

)

Try this out

<?php
    $hours_arr = array();
    foreach($proj_time as $item){
        if(!isset($hours_arr [$item['project_id']]) || $hours_arr [$item['project_id']]['item_value'] != $item['item_value']) {     
            $hours_arr [$item['project_id']]['item_value'] = $item['item_value'];
            $hours_arr [$item['project_id']]['hours'][] = $item['hours'];
        } else {
            $hours_arr [$item['project_id']]['hours'][0] += $item['hours'];
        }
    }